The present disclosure relates to subterranean operations and, more particularly, to systems and methods for extracting and analyzing formation fluids from solids (e.g., cuttings) circulated out of a subterranean formation.
The performance of subterranean operations entails various steps, each using a number of devices. Many subterranean operations entail introducing one or more treatment fluids into the subterranean formation. For instance, drilling operations play an important role when developing oil, gas or water wells or when mining for minerals and the like. During the drilling operations, a drill bit passes through various layers of earth strata as it descends to a desired depth. During the drilling process, the drill bit generates drill cuttings as it forms the well bore. Drill cuttings consist of small pieces of shale and rock. The drill cuttings, as well as other particulate solids in the well bore (e.g., fines), are carried in a return flow stream of the drilling fluid back to the well drilling platform. They are then separated from the bulk of the drilling fluid via conventional separators such as shale shakers, mud cleaners, and centrifuges. Some shale shakers filter coarse material from the drilling fluid while other shale shakers remove finer particles from the drilling fluid. After removing the solids therefrom, the drilling fluid may be re-used in the drilling process.
Properties of the drilling fluid are typically monitored at a well site during drilling operations, for example, to measure hydrocarbon gas concentrations as the drilling fluid is circulated out of the well bore. The level of the hydrocarbon gas may affect decisions regarding how the well is to be drilled as well as the safety of the drilling rig and personnel involved. Moreover, the concentration of hydrocarbon gases and other components present in the drilling fluid may be indicative of the characteristics of the formation being drilled, reservoir fluids in the formation, and/or the drilling environment. Accordingly, the analysis of drilling fluids and the changes they undergo during drilling operations may be important to the methods of drilling as well as the efficiency of the drilling operations.
One method for collecting and analyzing hydrocarbon gas concentrations at a well site involves the use of a “gas trap” to collect gases released from the drilling fluid and/or solids suspended therein. A rotor within a vessel is submerged into the drilling fluid as the drilling fluid exits the well bore. The drilling fluid is agitated as it enters into and exits out of the vessel and some of the gases dissolved therein evaporate and escape the confines of the fluid. These vaporized gases are then collected and processed by analytical methods to determine the presence and levels of hydrocarbons and other components. However, the accuracy and/or effectiveness of these methods may depend upon whether various components in the sample are readily vaporized and/or separated from the solid and liquid phases of the sample. If a particular component is less volatile or labile, it may not be present in a gas phase sample at all or in a disproportionate amount to the total amount of that component. Correction coefficients are sometimes applied to analytical results to account for incomplete vaporization of a sample or its components, but often these coefficients themselves may not accurately account for actual testing conditions, calibration of equipment, or other variables in a particular application.
Often formation solids, such as drill cuttings or other particulate material from a subterranean formation suspended in a drilling fluid may provide useful information about the subterranean formation from which they came and/or the status of various subterranean operations that have been performed in the formation (e.g., drilling operations). For example, such solids contain small amounts of the formation fluids (e.g., oil, water, etc.) of interest that are present in the formation. The permeability, porosity, rock composition, and/or other properties of the solids themselves also may be pertinent to a number of decisions about operations at the well site. In conventional methods of analysis, drill cuttings suspended in a drilling fluid sample may be filtered or otherwise separated from the drilling fluid when it is circulated to the surface. Often, the analysis of the drill cuttings themselves is limited to a visual inspection. In some cases, such drill cuttings may be sent to an offsite laboratory for further analysis. Such laboratory analysis typically involves a two-step process. First, the cuttings may be placed in an airtight container for some period of time and gases are permitted to evolve from the cuttings. The composition of these gases are then analyzed in a headspace analysis. Then, the remaining cuttings may be subjected to a solvent extraction process (for example, using a Sohxlet extractor) to remove formation fluids from the cuttings for analysis. However, the laboratory solvent extractions typically used in this analysis often take several hours (and in some cases multiple days) to complete.
While embodiments of this disclosure have been depicted and described and are defined by reference to example embodiments of the disclosure, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure.